In somatic cells, tubulin acetylation specifically occurs on lysine 40 of alpha tubulin following MT assembly and this post-translational modification was previously documented to be abundantly represented in stable microtubules(Barlan and Gelfand, 2010)

In somatic cells, tubulin acetylation specifically occurs on lysine 40 of alpha tubulin following MT assembly and this post-translational modification was previously documented to be abundantly represented in stable microtubules(Barlan and Gelfand, 2010). stable cytoplasmic MTs. These results demonstrate that the PADI6/CPL superstructure plays a key role in regulating MT-mediated organelle positioning and movement. Keywords:Cytoplasmic lattice, PADI6, Tubulin, Acetylated microtubule, Spindle, Organelle redistribution, Endoplasmic reticulum, Mitochondria, Oocyte maturation == Introduction == While the role of MTs and associated motor proteins in non-mammalian oocyte and early embryonic development is well documented (Elinson and Rowning, 1988;Gard, 1991;Lane and Allan, 1999;Lessman, 1987;Schroeder and Gard, 1992;Yisraeli et al., 1990), less is known about the MT network during early mammalian development. However, several mouse studies have shown that MT are required for formation of MT organizing centers and the meiotic spindle apparatus, polar body extrusion, pronuclear migration, and mitotic spindle formation in early embryos (Calarco-Gillam et al., 1983;Maro et al., 1990;Maro and Verlhac, 2002;Schatten et al., 1985) More recently, oocyte MTs have also been found to drive endoplasmic reticulum (ER) and mitochondrial re-targeting during oocyte maturation (FitzHarris et al., 2007;Mehlmann et al., 1995;Van Blerkom, 1991;Van Blerkom and Runner, 1984). MT mediated organelle transport is facilitated by molecular motor proteins such as the kinesins, which move along the MT from the minus end to the plus end, and dynein, which moves in the opposite direction(Hirokawa et al., 1998). Regulation of ATP-ase dependent motor activity is mediated by a wide range of factors including MT-associated proteins, cell cycle regulatory factors, DRAK2-IN-1 and, more recently, tubulin acetylation(Hammond et al., 2008). In somatic cells, tubulin acetylation specifically occurs on lysine 40 of alpha tubulin following MT assembly and this post-translational modification was previously documented to be abundantly represented in stable microtubules(Barlan and Gelfand, 2010). Interestingly, tubulin acetylation has also recently been found by several groups to play a critical DRAK2-IN-1 role in the trafficking of cellular cargo DRAK2-IN-1 by both dynein and by kinesin (Cambray-Deakin et al., 1988;Chen et al., 2010;Friedman et al., 2010). In mammalian oocytes, acetylated tubulin has also previously been associated with stable microtubules EGR1 at the spindle poles, however, a potential role in cytoplasmic organelle redistribution has not been previously investigated(Schatten et al., 1985). We have previously characterized a novel maternal effect gene, peptidylarginine deiminase 6 (PADI6), and found that this oocyte-and early embryo-restricted protein localizes to (Wright et al., 2003), and DRAK2-IN-1 is required for the formation of, the cytoplasmic lattices (CPLs), a highly abundant poorly-defined structure that is unique to mammalian oocytes and preimplantaion embryos (Esposito et al., 2007). Additionally, we found that the PADI6/CPLs complex appear to contain ribosomal components and to play a role in embryonic genome activation (Yurttas et al., 2008). Recently, we carried out a non-biased Triton X-100 differential solubility screen of wild-type andPadi6-null oocytes to identify other CPL-associated factors and found that -tubulin also seems to be associated with the lattices. In this report we have tested this hypothesis and present experimental evidence indicating that tubulin associates with PADI6 at the CPLs. Further, we also show that loss of the PADI6/CPL superstructure inPadi6-null mice significantly affects ER and mitochondrial positioning, and organelle reorganization during maturation. Next, through use of drugs that alter MT stability and MT motor activity, we show that the ER and mitochondria appear to be disconnected from MTs in PADI6-null oocytes. Finally we provide mechanistic insight to these results by showing that levels of acetylated tubulin are severely depleted in PADI6-null oocytes. These findings indicate that the oocyte PADI6/CPL superstructure DRAK2-IN-1 has a much broader function than previously realized in that they appear to be directly involved in facilitating key MT-mediated events during mammalian oogenesis. == Results and Discussion == == -Tubulin Co-localizes with PADI6 at the Oocyte CPLs == We have previously.